Food-limited growth of larval Atlantic herring Clupea harengus recurrently observed in a coastal nursery area

Matthias Paulsen,Arne M Malzahn,Catriona Clemmesen,Cornelius Hammer,Patrick Polte

doi:10.1186/s10152-016-0470-y

Abstract

Food-limited growth of larval fish, defined as growth rates lower than observed in other habitats or from laboratory experiments at a given temperature, is rarely reported in field studies. This would imply that either larval fishes are living in an environment characterized by plenty of food, that nutritional condition selective mortality (i.e., eliminating the weak) is very strong, or this impression is caused by misinterpretation of data concerning e.g., poor taxonomical resolution of potential prey items, i.e., total potential prey abundance is high, but positively selected food is actually scarce. We analyzed RNA:DNA derived growth rates of herring larvae (Clupea harengus L.) and taxonomically differentiated prey field data of six consecutive spring seasons from the Kiel Canal, an artificial waterway in northern Germany, in order to test if food-limited growth in larval fish can occur recurrently in coastal habitats. In all years analyzed, larval growth rates decreased simultaneously with prey abundance at the end of each larval season. Furthermore, larval growth rates were observed to be lower than mean growth rates observed in another herring larvae nursery area at temperatures above 15 °C. Asymptotic relationships between prey abundance and larval growth rates were observed, further supporting the hypothesis of food-limitation. As larval growth was best explained by the abundance of the numerically dominant calanoid copepod Eurytemora affinis, the paramount importance of the dominant prey item is highlighted. We conclude that food limitation can be a severe and re-occurring issue for larval fish in coastal habitats, and that certain prey items play a crucial role in determining larval growth rates, and therefore potentially recruitment.

Highlights

Over a century ago Hjort [35] hypothesized that the nutrition of first feeding larvae is an important recruitment-driving factor
The zooplankton community in the Kiel Canal was dominated by Eurytemora affinis, Acartia tonsa and cirriped nauplii (Table 1)
Eurytemora affinis was the numerically dominant species among the copepods found in the Kiel Canal (Fig. 2; Table 1)

Summary

Introduction

Over a century ago Hjort [35] hypothesized that the nutrition of first feeding larvae is an important recruitment-driving factor. Generations of fishery scientists worked on this issue, but it took decades until they started “emerging from Hjort’s shadow” [39], interpreting the issue of larval nutrition in a broader context. This includes biotic as well as abiotic factors influencing the nutritional situation for fish larvae, and focusing on the time of first feeding (e.g., [3, 10, 19, 50]). Small waterbodies and low water depths are typical for such areas, leading to strong short-term changes in temperature during spring time (e.g., [24, 52]), potentially with qualitative and quantitative implications for prey availability [2]

Methods

Results

Conclusion